Pub Date : 2026-05-01Epub Date: 2025-11-28DOI: 10.1016/j.euromechflu.2025.204422
Paul A. Jarvis , Allan Fries , Carolina Diaz-Vecino , Jonathan Lemus , Amanda Clarke , Irene Manzella , Jeremy Phillips , Costanza Bonadonna
Gravity currents are stratified shear flows common in various geophysical settings. During propagation, mixing between the current and the ambient fluid can occur via Kelvin–Helmholtz instabilities, leading to the formation of billows (vortices) on the current surface. Although the Kelvin–Helmholtz instability has implications for the transport of heat, solutes and sediments, the properties of the billows remain poorly quantified, particularly for free-surface gravity currents. This study presents laboratory experiments on buoyant, full-depth, lock-release gravity currents propagating at a free surface during the slumping regime. By varying the density contrast, we show that current propagation speeds and mean shapes align with two-layer shallow water theory, with most of the fluid contained in a temporally thinning, spatially uniform thick head. Kelvin–Helmholtz billows consistently form at the current front, becoming more coherent with increasing current velocity. We find that billows are generated at intervals equal to the time required for the current to advance a distance equal to its thickness, and they propagate forward at 25% of the current speed. Billows also undergo merging, with spacing approaching the total flow depth. Volume-based entrainment coefficients increase with Reynolds number, mirroring trends in basal currents. These findings quantify key properties of finite-amplitude Kelvin–Helmholtz billows in free-surface gravity currents and provide a foundation for understanding mixing and transport in environmental stratified shear flows.
{"title":"Kelvin–Helmholtz instabilities and mixing in surface-propagating gravity currents","authors":"Paul A. Jarvis , Allan Fries , Carolina Diaz-Vecino , Jonathan Lemus , Amanda Clarke , Irene Manzella , Jeremy Phillips , Costanza Bonadonna","doi":"10.1016/j.euromechflu.2025.204422","DOIUrl":"10.1016/j.euromechflu.2025.204422","url":null,"abstract":"<div><div>Gravity currents are stratified shear flows common in various geophysical settings. During propagation, mixing between the current and the ambient fluid can occur via Kelvin–Helmholtz instabilities, leading to the formation of billows (vortices) on the current surface. Although the Kelvin–Helmholtz instability has implications for the transport of heat, solutes and sediments, the properties of the billows remain poorly quantified, particularly for free-surface gravity currents. This study presents laboratory experiments on buoyant, full-depth, lock-release gravity currents propagating at a free surface during the slumping regime. By varying the density contrast, we show that current propagation speeds and mean shapes align with two-layer shallow water theory, with most of the fluid contained in a temporally thinning, spatially uniform thick head. Kelvin–Helmholtz billows consistently form at the current front, becoming more coherent with increasing current velocity. We find that billows are generated at intervals equal to the time required for the current to advance a distance equal to its thickness, and they propagate forward at 25% of the current speed. Billows also undergo merging, with spacing approaching the total flow depth. Volume-based entrainment coefficients increase with Reynolds number, mirroring trends in basal currents. These findings quantify key properties of finite-amplitude Kelvin–Helmholtz billows in free-surface gravity currents and provide a foundation for understanding mixing and transport in environmental stratified shear flows.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204422"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents a comprehensive numerical investigation of the melting behavior of a phase change material during heat transfer and storage. This material is located in an inclined enclosure filled with nanofluid, under non-uniform wall heating conditions. For the nanofluid medium, the influence of natural convection and volumetric thermal radiation is considered using real radiative properties of nanoparticles. The Lattice Boltzmann Method is utilized to simulate the coupled heat transfer and phase change processes. The effects of Planck numbers ( = 0.01–1), Rayleigh numbers ( = 104 and 105), and inclination angles ( = 0°–90°) are examined at different times to assess temperature distribution, melting front propagation, velocity profile, liquid fraction, and total heat transfer performance. The results show that at the highest Planck number ( = 1), natural convection dominates, with melting starting from boundaries aligned with the heated nanofluid flow. However, at Planck numbers less than 0.1, radiation significantly enhances the temperature distribution and melting rate, resulting in up to 8.3 and 7.5 times increases in the liquid fraction and total Nusselt number, respectively. At = 1, the inclination angle of 0° yielded the highest melting performance with a liquid fraction of 31 % and 22 % for = 104 and 105, respectively. While at = 0.01, the inclination angle of 45° achieved the maximum melting with values exceeding 60 % due to the intensified radiative heat transfer and enhancement of the total Nusselt number by about 8 times. The interplay between radiation intensity and enclosure angle offers an influential mechanism for enhancing thermal performance. These findings provide valuable insights into the optimized design of advanced latent heat storage systems under multi-mode heat transfers.
{"title":"PCM energy storage considering nanofluid volumetric radiation and natural convection in an inclined non-uniformly heated enclosure: LBM simulation","authors":"Masoud Sobhani , Javad Abolfazli Esfahani , Hashem Ahmadi Tighchi","doi":"10.1016/j.euromechflu.2025.204444","DOIUrl":"10.1016/j.euromechflu.2025.204444","url":null,"abstract":"<div><div>This study presents a comprehensive numerical investigation of the melting behavior of a phase change material during heat transfer and storage. This material is located in an inclined enclosure filled with nanofluid, under non-uniform wall heating conditions. For the nanofluid medium, the influence of natural convection and volumetric thermal radiation is considered using real radiative properties of nanoparticles. The Lattice Boltzmann Method is utilized to simulate the coupled heat transfer and phase change processes. The effects of Planck numbers (<span><math><mi>Pl</mi></math></span> = 0.01–1), Rayleigh numbers (<span><math><mi>Ra</mi></math></span> = 10<sup>4</sup> and 10<sup>5</sup>), and inclination angles (<span><math><mi>γ</mi></math></span> = 0°–90°) are examined at different times to assess temperature distribution, melting front propagation, velocity profile, liquid fraction, and total heat transfer performance. The results show that at the highest Planck number (<span><math><mi>Pl</mi></math></span> = 1), natural convection dominates, with melting starting from boundaries aligned with the heated nanofluid flow. However, at Planck numbers less than 0.1, radiation significantly enhances the temperature distribution and melting rate, resulting in up to 8.3 and 7.5 times increases in the liquid fraction and total Nusselt number, respectively. At <span><math><mi>Pl</mi></math></span> = 1, the inclination angle of 0° yielded the highest melting performance with a liquid fraction of 31 % and 22 % for <span><math><mi>Ra</mi></math></span>= 10<sup>4</sup> and 10<sup>5</sup>, respectively. While at <span><math><mi>Pl</mi></math></span> = 0.01, the inclination angle of 45° achieved the maximum melting with values exceeding 60 % due to the intensified radiative heat transfer and enhancement of the total Nusselt number by about 8 times. The interplay between radiation intensity and enclosure angle offers an influential mechanism for enhancing thermal performance. These findings provide valuable insights into the optimized design of advanced latent heat storage systems under multi-mode heat transfers.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204444"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-11-28DOI: 10.1016/j.euromechflu.2025.204425
Raju Sen, Rishi Raj Kairi
The present work investigates the concentration profile of a passive contaminant in Casson biofluid flow through an electrically actuated medium. Specifically, we examine buoyancy-driven unsteady solute dispersion in electroosmotic electromagnetohydrodynamic flow within a microchannel. Also, the solute transport is influenced by the presence of slip-dependent zeta potential and temperature-induced heat sources. At the boundary, a first-order heterogeneous reaction governs the behavior of the tracer concentration. The time-dependent convection–diffusion equation is tackled by an advanced numerical scheme, Aris’s method of moments, to frame the moment equations, which are then solved by an implicit finite difference scheme. The first four central moments, expressed through a Hermite polynomial, are used to calculate the tracer’s mean concentration distribution. The results indicate that with enhanced internal heating and buoyancy force dispersion of solute increased, and thus, the peak of the mean concentration reduced. Under combined flow (steady + unsteady), the dispersion coefficients of the solute are hardly adjusted by the magnetic influence for slip-independent zeta potential. However, the effect of magnetic damping is comparatively stronger for slip-dependent zeta potential. In the presence of a weak internal heat source, for the small Casson parameter, the kurtosis approaches a Gaussian distribution, while for strong internal heating, the kurtosis stays negative throughout the chosen range, indicating a non-Gaussian behavior. In particular, an appropriate variation of thermally driven solute dispersion will provide much-needed control to biochemical reactions and diagnostics integrated into lab-on-a-chip devices and the separation of chemical species, and hence, speed up medical test results and make them reliable.
{"title":"Electroosmotic-driven unsteady mass transport of non-Newtonian fluids flow through a microchannel under the influence of thermal buoyancy and slip-induced zeta potential","authors":"Raju Sen, Rishi Raj Kairi","doi":"10.1016/j.euromechflu.2025.204425","DOIUrl":"10.1016/j.euromechflu.2025.204425","url":null,"abstract":"<div><div>The present work investigates the concentration profile of a passive contaminant in Casson biofluid flow through an electrically actuated medium. Specifically, we examine buoyancy-driven unsteady solute dispersion in electroosmotic electromagnetohydrodynamic flow within a microchannel. Also, the solute transport is influenced by the presence of slip-dependent zeta potential and temperature-induced heat sources. At the boundary, a first-order heterogeneous reaction governs the behavior of the tracer concentration. The time-dependent convection–diffusion equation is tackled by an advanced numerical scheme, Aris’s method of moments, to frame the moment equations, which are then solved by an implicit finite difference scheme. The first four central moments, expressed through a Hermite polynomial, are used to calculate the tracer’s mean concentration distribution. The results indicate that with enhanced internal heating and buoyancy force dispersion of solute increased, and thus, the peak of the mean concentration reduced. Under combined flow (steady + unsteady), the dispersion coefficients of the solute are hardly adjusted by the magnetic influence for slip-independent zeta potential. However, the effect of magnetic damping is comparatively stronger for slip-dependent zeta potential. In the presence of a weak internal heat source, for the small Casson parameter, the kurtosis approaches a Gaussian distribution, while for strong internal heating, the kurtosis stays negative throughout the chosen range, indicating a non-Gaussian behavior. In particular, an appropriate variation of thermally driven solute dispersion will provide much-needed control to biochemical reactions and diagnostics integrated into lab-on-a-chip devices and the separation of chemical species, and hence, speed up medical test results and make them reliable.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204425"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-30DOI: 10.1016/j.euromechflu.2025.204441
M.S. Faltas , E.A. Ashmawy , Samar A. Mahrous , M. Magdy El Sayed , Kareem E. Ragab
This study investigates the quasi-steady axisymmetric thermophoretic motion of a spherical particle partially submerged at the flat interface of a semi-infinite Brinkman medium. The analysis is conducted under the assumptions of small Reynolds and Péclet numbers, while the capillary number is considered sufficiently small to preserve the flatness of the interface. The specific case of a contact angle with the flat surface is examined. To avoid singularities at the contact line, the Knudsen number is assumed to lie within the slip-flow regime. Analytical expressions are derived for the thermophoretic velocity and force acting on the half-submerged particle. Graphical results illustrate the influence of parameters such as Fourier thermal conductivity ratio, Knudsen number, medium permeability, frictional slip, and thermal stress slip. Furthermore, the limiting behavior corresponding to thermophoresis in a classical viscous fluid is discussed. Since the present solution is exact, the case of a contact angle also serves as a benchmark for validating numerical solutions at other contact angles. The findings are relevant to applications involving particle manipulation at fluid–porous interfaces, such as targeted drug delivery across biological membranes, pollutant transport at soil–air boundaries, and the design of microfluidic systems for controlled colloidal assembly.
{"title":"Thermophoresis of a spherical particle straddling a flat interface in a Brinkman medium at a 90° contact angle","authors":"M.S. Faltas , E.A. Ashmawy , Samar A. Mahrous , M. Magdy El Sayed , Kareem E. Ragab","doi":"10.1016/j.euromechflu.2025.204441","DOIUrl":"10.1016/j.euromechflu.2025.204441","url":null,"abstract":"<div><div>This study investigates the quasi-steady axisymmetric thermophoretic motion of a spherical particle partially submerged at the flat interface of a semi-infinite Brinkman medium. The analysis is conducted under the assumptions of small Reynolds and Péclet numbers, while the capillary number is considered sufficiently small to preserve the flatness of the interface. The specific case of a <span><math><mrow><mn>90</mn><mo>°</mo></mrow></math></span> contact angle with the flat surface is examined. To avoid singularities at the contact line, the Knudsen number is assumed to lie within the slip-flow regime. Analytical expressions are derived for the thermophoretic velocity and force acting on the half-submerged particle. Graphical results illustrate the influence of parameters such as Fourier thermal conductivity ratio, Knudsen number, medium permeability, frictional slip, and thermal stress slip. Furthermore, the limiting behavior corresponding to thermophoresis in a classical viscous fluid is discussed. Since the present solution is exact, the case of a <span><math><mrow><mn>90</mn><mo>°</mo></mrow></math></span> contact angle also serves as a benchmark for validating numerical solutions at other contact angles. The findings are relevant to applications involving particle manipulation at fluid–porous interfaces, such as targeted drug delivery across biological membranes, pollutant transport at soil–air boundaries, and the design of microfluidic systems for controlled colloidal assembly.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204441"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-16DOI: 10.1016/j.euromechflu.2025.204440
Siyi Li , Zihao Zhu , Lei Xie , Yaguang Xie , Ruonan Wang , Qiang Du , Junqiang Zhu
Instabilities in rotor–stator cavities significantly influence flow dynamics and heat transfer processes within aerospace propulsion systems. Among these instabilities, the circular waves manifests within the stator boundary layer and exhibits transient behavior highly sensitive to disturbances in the basic state. To elucidate the underlying mechanisms driving this transient phenomenon, through direct numerical simulation (DNS), we systematically imposed impulsive changes and harmonic modulations on the rotation speed of the rotor, thereby inducing various types of disturbances. Our findings reveal that the emergence of circular waves is triggered by these disturbances, with the waves’ characteristics displaying marked sensitivity to the nature of the disturbances. Specifically, increasing the disturbance frequency leads to an upward migration of the circular waves’ radial position. The energy and radial extent of the circular waves exhibit a trend of first increasing and then decreasing as the disturbance frequency increases. Moreover, as the disturbance amplitude increases, the radial extent occupied by the circular waves expands, while the midpoint of their radial position remains unaltered. We further identified that when a hub rotating with the rotor, circular waves can become self-sustaining under certain conditions. Specifically, when the gap ratio (, where is the radius of the hub, is the radius of the shroud, is the half of the gap between the rotor and stator) and rotational Reynolds number (, where refers to the rotational speed of the rotor, and refers to the kinematic viscosity) are sufficiently large, disturbances on the stator side can migrate through the hub, amplify, and form disturbances on the rotor side, subsequently re-exciting circular waves on the stator. Through linear stability analysis, we determined the boundary in the parameter domain that delineates conditions for self-sustaining circular waves. This study provides a comprehensive investigation into the behavior of circular waves, shedding new light on their complex dynamics within rotor–stator cavities.
{"title":"Direct numerical simulation and linear stability analysis of circular waves in the stator boundary layer of rotor–stator cavity","authors":"Siyi Li , Zihao Zhu , Lei Xie , Yaguang Xie , Ruonan Wang , Qiang Du , Junqiang Zhu","doi":"10.1016/j.euromechflu.2025.204440","DOIUrl":"10.1016/j.euromechflu.2025.204440","url":null,"abstract":"<div><div>Instabilities in rotor–stator cavities significantly influence flow dynamics and heat transfer processes within aerospace propulsion systems. Among these instabilities, the circular waves manifests within the stator boundary layer and exhibits transient behavior highly sensitive to disturbances in the basic state. To elucidate the underlying mechanisms driving this transient phenomenon, through direct numerical simulation (DNS), we systematically imposed impulsive changes and harmonic modulations on the rotation speed of the rotor, thereby inducing various types of disturbances. Our findings reveal that the emergence of circular waves is triggered by these disturbances, with the waves’ characteristics displaying marked sensitivity to the nature of the disturbances. Specifically, increasing the disturbance frequency leads to an upward migration of the circular waves’ radial position. The energy and radial extent of the circular waves exhibit a trend of first increasing and then decreasing as the disturbance frequency increases. Moreover, as the disturbance amplitude increases, the radial extent occupied by the circular waves expands, while the midpoint of their radial position remains unaltered. We further identified that when a hub rotating with the rotor, circular waves can become self-sustaining under certain conditions. Specifically, when the gap ratio (<span><math><mrow><mi>γ</mi><mo>=</mo><mrow><mo>(</mo><mi>b</mi><mo>−</mo><mi>a</mi><mo>)</mo></mrow><mo>/</mo><mi>H</mi></mrow></math></span>, where <span><math><mi>a</mi></math></span> is the radius of the hub, <span><math><mi>b</mi></math></span> is the radius of the shroud, <span><math><mi>H</mi></math></span> is the half of the gap between the rotor and stator) and rotational Reynolds number (<span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mi>Ω</mi><msup><mrow><mi>b</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><mi>ν</mi></mrow></math></span>, where <span><math><mi>Ω</mi></math></span> refers to the rotational speed of the rotor, and <span><math><mi>ν</mi></math></span> refers to the kinematic viscosity) are sufficiently large, disturbances on the stator side can migrate through the hub, amplify, and form disturbances on the rotor side, subsequently re-exciting circular waves on the stator. Through linear stability analysis, we determined the boundary in the <span><math><mrow><mo>(</mo><mi>R</mi><mi>e</mi><mo>,</mo><mi>γ</mi><mo>)</mo></mrow></math></span> parameter domain that delineates conditions for self-sustaining circular waves. This study provides a comprehensive investigation into the behavior of circular waves, shedding new light on their complex dynamics within rotor–stator cavities.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204440"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-08DOI: 10.1016/j.euromechflu.2025.204442
Yigan Zhang, Zehui Qu, Yonghao Ye, Baiyan He, Huaping Liu
Tip-leakage vortex (TLV) and TLV cavitation have a significant negative impact on the efficiency and stability of hydraulic machinery. This study proposes an active flow control strategy based on tip water injection. The NACA0009 hydrofoil, with two representative tip clearance sizes of 2 mm and 10 mm, is employed to systematically investigate the influence of injection angle on TLV suppression. The SST-CC turbulence model and the ZGB cavitation model are used to capture unsteady cavitating flows. The results reveal that the water injection operates through two primary control mechanisms involving momentum mixing and channel blockage. These mechanisms collectively reduce the tip leakage flow velocity and increase the local pressure, thereby suppressing the development of the TLV and the associated cavitation. As the injection angle β increases, the blockage effect becomes more pronounced, thereby enhancing the suppression effect of the TLV. Under small clearance condition (2 mm), the water injection induces the multiple smaller TLV, which weakens the primary TLV strength. Under large clearance condition (10 mm), the water injection remains effective in reducing tip leakage velocity and suppressing TLV cavitation.
{"title":"Numerical investigation on the suppression mechanism of tip leakage vortex and cavitation via tip water injection","authors":"Yigan Zhang, Zehui Qu, Yonghao Ye, Baiyan He, Huaping Liu","doi":"10.1016/j.euromechflu.2025.204442","DOIUrl":"10.1016/j.euromechflu.2025.204442","url":null,"abstract":"<div><div>Tip-leakage vortex (TLV) and TLV cavitation have a significant negative impact on the efficiency and stability of hydraulic machinery. This study proposes an active flow control strategy based on tip water injection. The NACA0009 hydrofoil, with two representative tip clearance sizes of 2 mm and 10 mm, is employed to systematically investigate the influence of injection angle on TLV suppression. The SST-CC turbulence model and the ZGB cavitation model are used to capture unsteady cavitating flows. The results reveal that the water injection operates through two primary control mechanisms involving momentum mixing and channel blockage. These mechanisms collectively reduce the tip leakage flow velocity and increase the local pressure, thereby suppressing the development of the TLV and the associated cavitation. As the injection angle <em>β</em> increases, the blockage effect becomes more pronounced, thereby enhancing the suppression effect of the TLV. Under small clearance condition (2 mm), the water injection induces the multiple smaller TLV, which weakens the primary TLV strength. Under large clearance condition (10 mm), the water injection remains effective in reducing tip leakage velocity and suppressing TLV cavitation.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204442"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-18DOI: 10.1016/j.euromechflu.2025.204447
Yupeng Liao , Changjun Li , Wenlong Jia , Juncheng Mu , Jie He , Fan Yang , Qiaojing Huang
This paper proposes a new segregated algorithm named SIMPLE-Revised with Residual Coupling (SIMPLER*) for simulating the two-phase flow of gas-condensate in pipelines. The full coupling of velocity and pressure is ensured by introducing the momentum equation residual and the double inner iteration, which improves the computational efficiency while solving the issues of velocity-pressure decoupling and pressure overcorrection in the traditional Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. The adaptive time-stepping method is employed to reduce computational costs in transient simulations. The performance of SIMPLE, SIMPLE-Revised-Revised (SIMPLERR), and SIMPLER* algorithms is comprehensively compared. Validation across four classical benchmark tests confirms the superior robustness and numerical stability of SIMPLER*, which exhibits lower numerical diffusion and remains oscillation-free under strong pressure discontinuities. Subsequent steady-state and transient engineering cases demonstrate that the computational efficiency of the SIMPLER* algorithm is significantly better than that of the SIMPLE and SIMPLERR algorithms, both in coarse and fine grids. The proposed "adaptive time-stepping + SIMPLER* algorithm" combination method greatly reduces the computational overhead while ensuring the accuracy of the solution, providing an efficient and reliable solution for the transient simulation of complex two-phase flow with phase change.
{"title":"Insight into the numerical efficiency and stability of a residual-coupled segregated solver for gas-condensate two-phase flow in pipelines: An algorithmic study","authors":"Yupeng Liao , Changjun Li , Wenlong Jia , Juncheng Mu , Jie He , Fan Yang , Qiaojing Huang","doi":"10.1016/j.euromechflu.2025.204447","DOIUrl":"10.1016/j.euromechflu.2025.204447","url":null,"abstract":"<div><div>This paper proposes a new segregated algorithm named SIMPLE-Revised with Residual Coupling (SIMPLER*) for simulating the two-phase flow of gas-condensate in pipelines. The full coupling of velocity and pressure is ensured by introducing the momentum equation residual and the double inner iteration, which improves the computational efficiency while solving the issues of velocity-pressure decoupling and pressure overcorrection in the traditional Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. The adaptive time-stepping method is employed to reduce computational costs in transient simulations. The performance of SIMPLE, SIMPLE-Revised-Revised (SIMPLERR), and SIMPLER* algorithms is comprehensively compared. Validation across four classical benchmark tests confirms the superior robustness and numerical stability of SIMPLER*, which exhibits lower numerical diffusion and remains oscillation-free under strong pressure discontinuities. Subsequent steady-state and transient engineering cases demonstrate that the computational efficiency of the SIMPLER* algorithm is significantly better than that of the SIMPLE and SIMPLERR algorithms, both in coarse and fine grids. The proposed \"adaptive time-stepping + SIMPLER* algorithm\" combination method greatly reduces the computational overhead while ensuring the accuracy of the solution, providing an efficient and reliable solution for the transient simulation of complex two-phase flow with phase change.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204447"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2025-12-23DOI: 10.1016/j.euromechflu.2025.204448
Bruno Thierry Nyatchouba Nsangue , Tang Hao , Mezoue Adiang Cyrille , Liuxiong Xu , Fuxiang Hu , Ruben Mouangue
The unsteady turbulent flow, the trawl codend, and the Bycatch reduction device (BRD) are characterized by a complex interaction. A thorough understanding of this interaction is crucial for minimizing bycatch, enhancing the escape probability of non-target species, and improving trawl selectivity. This study analyzes unsteady turbulent flow fields inside and around the bottom trawl codends equipped with BRDs, systematically exploring the reconstruction capabilities of three deep learning algorithms, involving Long Short-Term Memory (LSTM), Echo State Network (ESN), and Convolutional Neural Network-Long Short-Term Memory (CNN-LSTM). Extensive assessment encompasses the predictive reliability of the instantaneous flow fields, velocity ratio profiles, turbulent intensity, turbulent kinetic energy, Reynold stress, time series streamwise flow velocities, and training efficiency. Results indicate a full development of unsteady turbulent flow inside and around the codend without BRD, characterized by instantaneous shear layer instabilities and vortex shedding. In contrast, the codend-BRD system and water flow interaction generates two distinct regions with very low flow velocity fields behind it, characterized by vortex-shedding structures on the unsteady turbulent wake. The flow velocity deficit was greater inside the codend compared to that observed inside the combined codend-BRD system due to free water flow passage through the combined codend-BRD system due to the presence of BRD windows. A higher turbulent kinetic energy, greater momentum flux, and stronger turbulence intensities are observed inside and around the codend without BRD compared to the codend-BRD system. Additionally, the results indicate that ESN and CNN-LSTM exhibit a significant advantage in reconstructing unsteady turbulent flow parameters. The prediction of unsteady turbulent flow parameters indicates that all the three models are substantially consistent with the experimental data. However, LSTM is a judicious choice when solely the time series variables require prediction. These insights significantly advance the development of smart trawl nets, offering a pathway to enhance gear selectivity through data-driven design.
{"title":"Deep learning prediction of unsteady turbulent transformation pattern inside and around the interactions between a sorting grid and a trawl system","authors":"Bruno Thierry Nyatchouba Nsangue , Tang Hao , Mezoue Adiang Cyrille , Liuxiong Xu , Fuxiang Hu , Ruben Mouangue","doi":"10.1016/j.euromechflu.2025.204448","DOIUrl":"10.1016/j.euromechflu.2025.204448","url":null,"abstract":"<div><div>The unsteady turbulent flow, the trawl codend, and the Bycatch reduction device (BRD) are characterized by a complex interaction. A thorough understanding of this interaction is crucial for minimizing bycatch, enhancing the escape probability of non-target species, and improving trawl selectivity. This study analyzes unsteady turbulent flow fields inside and around the bottom trawl codends equipped with BRDs, systematically exploring the reconstruction capabilities of three deep learning algorithms, involving Long Short-Term Memory (LSTM), Echo State Network (ESN), and Convolutional Neural Network-Long Short-Term Memory (CNN-LSTM). Extensive assessment encompasses the predictive reliability of the instantaneous flow fields, velocity ratio profiles, turbulent intensity, turbulent kinetic energy, Reynold stress, time series streamwise flow velocities, and training efficiency. Results indicate a full development of unsteady turbulent flow inside and around the codend without BRD, characterized by instantaneous shear layer instabilities and vortex shedding. In contrast, the codend-BRD system and water flow interaction generates two distinct regions with very low flow velocity fields behind it, characterized by vortex-shedding structures on the unsteady turbulent wake. The flow velocity deficit was greater inside the codend compared to that observed inside the combined codend-BRD system due to free water flow passage through the combined codend-BRD system due to the presence of BRD windows. A higher turbulent kinetic energy, greater momentum flux, and stronger turbulence intensities are observed inside and around the codend without BRD compared to the codend-BRD system. Additionally, the results indicate that ESN and CNN-LSTM exhibit a significant advantage in reconstructing unsteady turbulent flow parameters. The prediction of unsteady turbulent flow parameters indicates that all the three models are substantially consistent with the experimental data. However, LSTM is a judicious choice when solely the time series variables require prediction. These insights significantly advance the development of smart trawl nets, offering a pathway to enhance gear selectivity through data-driven design.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204448"},"PeriodicalIF":2.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-11-12DOI: 10.1016/j.euromechflu.2025.204403
Xi-Hu Wu , Yuan Shen
In geophysical hydrodynamics, baroclinic instability refers to the process in which the perturbations absorb energy from potential energy of the mean flow. In this manuscript, we focus our attention on a nonlinear system modeling the propagation of the wave packet within a quasigeostrophic two-layer model in a baroclinic shear flow. With the aid of the generalized Darboux transformation method, we derive several types of the semi-rational solutions to explore bound states among the localized waves and multi-pole localized waves. On different backgrounds, the wave packet and the wave-induced modification of the basic flow manifest themselves as the bound states among multiple solitons/breathers, the bound states among a single soliton/breather component and the multi-pole solitons/breathers, and the bound states among two sets of the double-pole solitons. Physical dynamics of those bound-state nonlinear waves are discussed. We find that the bound states among the solitons/breathers exhibit periodic attractions or repulsions, while the bound states among the solitons/breathers and multi-pole solitons/breathers exhibit non-periodic interactions. This work may provide theoretical support and explanations for the complex and variable natural mechanisms underlying baroclinic instability.
{"title":"Bound states for a quasigeostrophic two-layer model in a baroclinic shear flow","authors":"Xi-Hu Wu , Yuan Shen","doi":"10.1016/j.euromechflu.2025.204403","DOIUrl":"10.1016/j.euromechflu.2025.204403","url":null,"abstract":"<div><div>In geophysical hydrodynamics, baroclinic instability refers to the process in which the perturbations absorb energy from potential energy of the mean flow. In this manuscript, we focus our attention on a nonlinear system modeling the propagation of the wave packet within a quasigeostrophic two-layer model in a baroclinic shear flow. With the aid of the generalized Darboux transformation method, we derive several types of the semi-rational solutions to explore bound states among the localized waves and multi-pole localized waves. On different backgrounds, the wave packet and the wave-induced modification of the basic flow manifest themselves as the bound states among multiple solitons/breathers, the bound states among a single soliton/breather component and the multi-pole solitons/breathers, and the bound states among two sets of the double-pole solitons. Physical dynamics of those bound-state nonlinear waves are discussed. We find that the bound states among the solitons/breathers exhibit periodic attractions or repulsions, while the bound states among the solitons/breathers and multi-pole solitons/breathers exhibit non-periodic interactions. This work may provide theoretical support and explanations for the complex and variable natural mechanisms underlying baroclinic instability.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"116 ","pages":"Article 204403"},"PeriodicalIF":2.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145517715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-11-19DOI: 10.1016/j.euromechflu.2025.204420
Lingyun Tian, Xiaoyang Xu
Near-surface underwater explosions in shallow water involve complex interactions among shock waves, free surfaces, and bottom boundaries, which significantly affect shock wave propagation and pressure distribution. These interactions pose challenges for damage assessment of marine and coastal structures. In this study, an improved smoothed particle hydrodynamics (SPH) method is developed to simulate near-surface underwater explosions in shallow water. The improvements include a density-continuity-based discretization, artificial viscosity, variable smoothing length, and a particle shifting technique, which mitigate tensile instability in the thin water layer near the free surface and enhance the accuracy of underwater explosion simulations. First, the proposed SPH method is applied to simulate TNT slab detonation and free-field underwater explosions. The effectiveness of the proposed method is validated by comparing simulation results with theoretical solutions. Then, an SPH model is developed to investigate shock wave evolution under the impact of surface boundary conditions in near-surface underwater explosions. Finally, the method is extended to simulate near-surface underwater explosions in shallow water, investigating the effects of bottom boundary inclination on shock wave reflection and bubble morphology. The results reveal that shallow charge depths enhance surface disturbances, while sloped boundaries induce asymmetric pressure focusing and bubble deformation. Overall, the improved SPH method demonstrates reliable capability in capturing shock wave propagation, reflection, surface disturbance, and bubble expansion in near-surface underwater explosions.
{"title":"An improved SPH method for simulating near-surface underwater explosions in shallow water","authors":"Lingyun Tian, Xiaoyang Xu","doi":"10.1016/j.euromechflu.2025.204420","DOIUrl":"10.1016/j.euromechflu.2025.204420","url":null,"abstract":"<div><div>Near-surface underwater explosions in shallow water involve complex interactions among shock waves, free surfaces, and bottom boundaries, which significantly affect shock wave propagation and pressure distribution. These interactions pose challenges for damage assessment of marine and coastal structures. In this study, an improved smoothed particle hydrodynamics (SPH) method is developed to simulate near-surface underwater explosions in shallow water. The improvements include a density-continuity-based discretization, artificial viscosity, variable smoothing length, and a particle shifting technique, which mitigate tensile instability in the thin water layer near the free surface and enhance the accuracy of underwater explosion simulations. First, the proposed SPH method is applied to simulate TNT slab detonation and free-field underwater explosions. The effectiveness of the proposed method is validated by comparing simulation results with theoretical solutions. Then, an SPH model is developed to investigate shock wave evolution under the impact of surface boundary conditions in near-surface underwater explosions. Finally, the method is extended to simulate near-surface underwater explosions in shallow water, investigating the effects of bottom boundary inclination on shock wave reflection and bubble morphology. The results reveal that shallow charge depths enhance surface disturbances, while sloped boundaries induce asymmetric pressure focusing and bubble deformation. Overall, the improved SPH method demonstrates reliable capability in capturing shock wave propagation, reflection, surface disturbance, and bubble expansion in near-surface underwater explosions.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"116 ","pages":"Article 204420"},"PeriodicalIF":2.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145615187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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